also: オフ・シーズン
noun
Refers to the period when a particular activity, tourism, or sport is not in its peak season.
オフシーズンはホテルが安くなる。
Hotels become cheaper in the off-season.
このリゾート地はオフシーズンでも楽しめる。
You can enjoy this resort even in the off-season.
シーズンオフ is a less common variant with the same meaning; オフシーズン is the standard form.
Loanword from English 'off-season'.